Taxonomy & naming
Enteromius niokoloensis was described by the French ichthyologist Jacques Daget in 1959, in a paper titled "Description de trois poissons nouveaux de la Gambie" — "Description of three new fishes from the Gambia" — placing it originally in the genus Barbus as Barbus niokoloensis. The species name derives from the Niokolo Koba National Park in southeastern Senegal, the area from which the type material was collected.
The Catalog of Fishes places the species in Enteromius, a large African genus that absorbed the bulk of sub-Saharan Barbus when the old catch-all genus Barbus sensu lato was progressively dismembered. Enteromius itself is a complex and polyphyletic assemblage in current ichthyological understanding, and ongoing molecular and morphological work continues to reorganise its constituent species; the valid combination for this species under current authority is Enteromius niokoloensis (Daget, 1959), with the parenthetical author marking its movement out of the original genus.
Morphology
Enteromius niokoloensis is a small barb, reaching a maximum of approximately 2 in standard length per FishBase. Like the broader genus, it has the typical cyprinid body plan — moderately compressed, with a subterminal mouth suited for picking invertebrates from the substrate. Fin-ray counts reported for the species include 11 dorsal soft rays and 8 anal soft rays.
Detailed meristic and colour descriptions are sparse in the published record accessible from this region; the species is known primarily from its original description and subsequent records from the river systems of western West Africa. As with many small African Enteromius, it is likely an unspectacular, silvery-bodied small barb, occupying the lower water column of its riverine habitat.
Habitat
The species is recorded from the upper and middle Gambia River, the Bafing River (a major tributary of the Senegal River in Guinea), and the Corubal River — river systems draining the Fouta Djallon highlands and the Guinea-Senegal borderlands into the Atlantic. Its distribution centres on the Niokolo Koba National Park area of southeastern Senegal, a protected savanna-woodland landscape bisected by the Gambia River.
FishBase characterises E. niokoloensis as a benthopelagic freshwater species of the lower water column, preferring deeper river stretches with weak to moderate current and heterogeneous sandy substrates. The rivers of this zone flow through Sahel-savanna and Guinea-savanna vegetation, experiencing marked wet and dry seasonality; water chemistry in these systems is generally soft to moderately mineralised, and temperatures follow tropical savanna patterns with warm conditions year-round.
Feeding
No detailed feeding studies specific to Enteromius niokoloensis are available in the accessible literature. As a benthopelagic small barb of the lower water column in sandy-bottomed West African rivers, it almost certainly takes the invertebrates — insect larvae, small crustaceans, worms and organic detritus — typical of generalist small Enteromius throughout the region.
In the aquarium, small African barbs of this type accept fine-grade flake and micro-pellet foods readily, and benefit from regular offerings of small live or frozen invertebrates such as bloodworm and brine shrimp nauplii. Data specific to this species' diet in the wild are sparse.
Mating
Enteromius niokoloensis, like all barbs, is an egg-scattering, non-guarding spawner. No courtship or reproductive observations specific to this species appear in the accessible literature, but the pattern for the genus is consistent: a driving male pursues a gravid female through the lower water column or over the sandy substrate, and eggs and milt are released together in brief lateral presses.
There is no nest, no pair bond, and no territory maintained beyond the brief act of spawning. Adults show no post-spawning interest in eggs or larvae. In seasonally variable West African river systems, spawning in wild populations is likely timed to the onset of the wet season, when rising water levels, warming temperatures and increased food availability trigger reproductive condition.
Breeding
No captive-breeding records for Enteromius niokoloensis are documented in the accessible hobby or scientific literature, and the species is not established in the aquarium trade. General principles for breeding small West African Enteromius apply: a separate shallow tank with soft, warm water, fine sandy or gravel substrate, and some plant cover or spawning mops would provide a suitable setup. Eggs are adhesive and scattered; adults should be removed after spawning to prevent predation on the eggs.
Fecundity and incubation times are not documented for this species specifically. As with other small savanna-zone barbs, larvae would be expected to require infusoria or other fine first foods before graduating to nauplii.
In the aquarium
Enteromius niokoloensis is not an established aquarium species and is essentially unknown in the hobby. Its small size — under 2 in standard length — and benthopelagic habits suggest it would be manageable in a modest biotope aquarium replicating the sandy lower reaches of a West African savanna river: a tank with a fine sand substrate, gentle to moderate flow, subdued lighting, and sparse cover from driftwood or leaf litter.
As with most small wild-caught West African barbs, it would best be maintained in a species group or with similarly sized, non-aggressive tankmates. Practical husbandry details remain undocumented for this species; hobbyists interested in West African cyprinids should consult biotope aquarium literature for general guidance on the region's conditions.
Conservation
Enteromius niokoloensis is assessed as Least Concern on the IUCN Red List (2022.2 update), reflecting its distribution across several river systems in West Africa — the Gambia, Senegal (via the Bafing), and Corubal — and the absence of documented major threats driving a range-wide decline. The Niokolo Koba National Park, where the species was first collected, provides some degree of habitat protection within its range.
The broader pressures on West African freshwater fish communities — seasonal river regulation, agricultural water extraction, artisanal fishing, and the degradation of riparian vegetation in the Sahel transition zone — are relevant background threats, though none is specifically documented as impacting this species. Its restricted range to a handful of river systems in this ecologically variable region warrants ongoing monitoring as savanna hydrology is increasingly affected by climate variability.